In order for orchid seeds to germinate, they rely on a special symbiotic fungus. Since symbiotic sowing under sterile conditions is complex and delicate, simple alternatives were researched. The result was asymbiotic sowing, with a culture medium replacing the mycorrhizal fungus. We explain here how to prepare this medium for sowing.
How do you prepare orchid growing medium yourself?
To prepare orchid medium yourself, you will need medium powder, distilled water, test tubes, a pressure cooker and agar-agar if necessary. Stir the granules into water, heat, fill test tubes, sterilize in a pressure cooker and allow to cool.
Equipment and material at a glance
For the sowing of orchid seeds to be successful, no laboratory equipment is required. With the following equipment the plan can succeed:
- Test tubes with heat-resistant stoppers
- Wire frame
- cooking pot
- Pressure cooker
- Postal scale for weighing nutrient medium powder
- Glass funnel
- Nourishing medium powder
- Distilled water
- Aluminum foil
Suitable nutrient medium powder is available from specialist retailers and online shops, such as the nutrient medium P6668 from Sigma. If you are willing to dig a little deeper into your pockets, you can choose instant media that is tailored to the specific type of orchid. The sowing medium SBL-A gets the seeds of Phalaenopsis and Vanda going, while SBL-C gets the seeds of Cattleya and Dendrobium in the mood to germinate.
Instructions for preparing culture medium
All vessels and tools are thoroughly cleaned and disinfected in advance. Then stir the nutrient medium powder weighed out using the postal scale into the distilled water and fill the solution into the cooking pot. Bring the liquid to the boil and simmer gently for 2 minutes. It is important to note that the solution does not foam.
Use the glass funnel to fill the liquid culture medium into the test tubes and loosely attach the heat-resistant plug. Place the culture vessels in the wire stand, cap each glass with an aluminum foil cap and place everything in the pressure cooker. Fill in the minimum amount of water permitted according to the manufacturer's instructions and close the pressure cooker.
The water is heated to 120 degrees to generate a pressure of 0.8 bar. This condition must be maintained for 15 minutes. Ideally, you let the test tubes cool overnight. Now screw the caps tight and label each jar. If no contamination has developed in the glass after a waiting period of 1 week, the culture medium can be used.
Tip
If the package insert indicates that the nutrient medium granules do not contain any gelling agent, please add this. Agar-agar, which can be bought inexpensively in the supermarket, has proven to work well in practice. A dosage of 6 to 7 grams per liter of water is usually appropriate.